Observabilité : journaux, indicateurs et traçage
Intégrez une journalisation complète, la collecte d’indicateurs et le traçage distribué pour comprendre en profondeur le comportement de votre application LLM.
Observabilité : journaux, indicateurs et traçage est une leçon LLM Apps in Production (RAG + Vector DB + Caching) gratuite sur CoddyKit. Ceci est la leçon 2 sur 4. Tu peux lire la leçon complète ci-dessous gratuitement — puis la pratiquer en direct dans le navigateur avec un éditeur de code intégré et un tuteur IA 24/7. Elle fait partie du parcours d'apprentissage LLM Apps in Production (RAG + Vector DB + Caching), et ta progression se synchronise sur le web et l'application CoddyKit. Le cours LLM Apps in Production (RAG + Vector DB + Caching) comprend 4 leçons au total.
Certaines parties de cette leçon n'ont pas encore été traduites et s'affichent en anglais.
What is Observability?
In this lesson, we'll explore observability, a crucial concept for managing complex software systems, especially LLM applications.
Observability means understanding the internal state of a system by examining the data it produces. Think of it as having X-ray vision into your application's behavior.
For LLM apps, this helps us answer critical questions like:
- Why is a request slow?
- Is the RAG retrieval working as expected?
- Are we incurring unexpected costs?
Logs: Recording Events
Logs are timestamped records of events that happen within your application. They are like a diary of your system's activities.
For LLM applications, logs are essential for:
- Tracking incoming user prompts.
- Storing responses from the LLM.
- Recording intermediate steps in a RAG pipeline (e.g., documents retrieved).
- Capturing errors or warnings.
They provide detailed contextual information for debugging and post-mortem analysis.
Logging LLM Interactions
Here's a simple Python example demonstrating how to log an LLM interaction. We're using Python's built-in logging module.
This helps you see exactly what prompts were sent and what responses were received, which is vital for debugging and improving your application.
import logging
logging.basicConfig(
level=logging.INFO,
format='%(asctime)s - %(levelname)s - %(message)s'
)
def call_llm(prompt):
logging.info(f"LLM Request: '{prompt[:40]}...' ")
# Simulate LLM processing
response = f"Simulated response to: {prompt}"
logging.info(f"LLM Response: '{response[:40]}...' ")
return response
if __name__ == "__main__":
user_prompt = "Explain observability simply."
result = call_llm(user_prompt)
print(f"Application output: {result}")Metrics: Measuring Performance
Metrics are numerical measurements collected over time, providing aggregated insights into your system's health and performance.
Unlike logs, which are individual events, metrics are typically quantitative values that can be visualized as graphs and dashboards. Key metrics for LLM apps include:
- Latency: How long it takes for the LLM to respond.
- Token Usage: Input/output tokens consumed per request.
- Error Rate: Percentage of failed LLM calls or RAG retrievals.
- Cache Hit Rate: How often cached responses are used.
Collecting Custom Metrics
You can collect custom metrics to understand specific aspects of your LLM application. This example shows how to track the number of LLM calls and their average latency.
In a real-world scenario, you'd send these metrics to a monitoring system like Prometheus or Datadog.
import time
class LLMMetrics:
def __init__(self):
self.total_calls = 0
self.total_latency = 0.0
def record_call(self, duration):
self.total_calls += 1
self.total_latency += duration
def get_avg_latency(self):
if self.total_calls == 0:
return 0.0
return self.total_latency / self.total_calls
metrics_store = LLMMetrics()
def call_llm_with_metrics(prompt):
start_time = time.time()
# Simulate LLM processing
time.sleep(0.05) # simulate 50ms work
response = f"Simulated reply to: {prompt}"
end_time = time.time()
metrics_store.record_call(end_time - start_time)
return response
if __name__ == "__main__":
print("Collecting LLM call metrics...")
call_llm_with_metrics("Hi")
call_llm_with_metrics("How are you?")
print(f"Total calls: {metrics_store.total_calls}")
print(f"Avg latency: {metrics_store.get_avg_latency():.3f}s")Tracing: Following Request Paths
Tracing is about following a single request as it flows through multiple services and components in a distributed system. This is especially vital for RAG applications that involve many steps: user input, embedding generation, vector DB lookup, LLM call, etc.
A trace visualizes the entire journey of a request, showing the exact path it took and the time spent in each operation.
Traces, Spans, and Context
A trace is a complete end-to-end journey of a request. It's composed of multiple spans.
- A span represents a single operation or unit of work within a trace (e.g., 'retrieve documents', 'call embedding model', 'invoke LLM').
- Spans have a parent-child relationship, forming a tree structure that shows dependencies.
- Context propagation ensures that a unique trace ID follows the request across different services, linking all related spans together.
This helps pinpoint bottlenecks or failures across microservices.
OpenTelemetry for Tracing
While implementing tracing from scratch is complex, tools like OpenTelemetry (an open-source observability framework) provide standardized ways to instrument your code.
You'd use OpenTelemetry SDKs to:
- Start a new trace when a request comes in.
- Create new spans for each significant operation (e.g., a function call to a vector database or an LLM API).
- Propagate the trace context to downstream services.
This allows you to visualize the full request flow in a tracing UI.
The Observability Triangle
Logs, metrics, and traces are often called the "observability triangle" because they offer complementary views of your system:
- Logs: The granular details and events.
- Metrics: The aggregated numbers and trends.
- Traces: The end-to-end journey of a request.
Together, they provide a comprehensive understanding of your LLM application's behavior, making it easier to diagnose issues, optimize performance, and ensure reliability in production.
Quick Check: Observability
You've learned about the three pillars of observability. Let's see if you can distinguish their primary uses.
Recap: Deep Insights
Congratulations! You've explored the world of observability for LLM applications.
- We defined observability as understanding internal system state from external data.
- We learned about logs for detailed event recording.
- We covered metrics for aggregated performance measurements.
- We understood traces for visualizing end-to-end request flows.
By integrating these three pillars, you gain powerful insights, enabling you to build more reliable, performant, and cost-efficient LLM systems.
Questions Fréquemment Posées
La leçon « Observabilité : journaux, indicateurs et traçage » est-elle gratuite ?
Oui — le texte complet de « Observabilité : journaux, indicateurs et traçage » est gratuit à lire ici sur le web. Pour la pratiquer de manière interactive (un éditeur de code intégré et un tuteur IA 24/7) et déverrouiller le reste du cours LLM Apps in Production (RAG + Vector DB + Caching), passe à CoddyKit PRO. Le cours LLM Apps in Production (RAG + Vector DB + Caching) comprend 4 leçons au total.
Qu'est-ce que j'apprendrai dans « Observabilité : journaux, indicateurs et traçage » ?
Intégrez une journalisation complète, la collecte d’indicateurs et le traçage distribué pour comprendre en profondeur le comportement de votre application LLM. Tu pratiques LLM Apps in Production (RAG + Vector DB + Caching) avec du code pratique que tu exécutes directement dans le navigateur, et un tuteur IA 24/7 répond à tes questions au fur et à mesure que tu avances dans la leçon.
Dois-je avoir de l'expérience pour commencer LLM Apps in Production (RAG + Vector DB + Caching) ?
Aucune expérience préalable n'est requise. LLM Apps in Production (RAG + Vector DB + Caching) sur CoddyKit est structuré pour les débutants jusqu'aux apprenants avancés, donc tu peux commencer ici ou depuis le début et avancer à ton rythme. Ceci est la leçon 2 sur 4.
Combien de temps prend la leçon « Observabilité : journaux, indicateurs et traçage » ?
La plupart des leçons CoddyKit prennent environ 5–10 minutes. Chacune est courte et interactive, tu progresses régulièrement et tu repiques exactement où tu t'es arrêté sur le web et l'app.
Peux-tu écrire et exécuter du code dans cette leçon LLM Apps in Production (RAG + Vector DB + Caching) ?
Oui. Chaque leçon LLM Apps in Production (RAG + Vector DB + Caching) inclut un éditeur de code intégré, tu écris et exécutes du vrai code directement dans ton navigateur et tu reçois des retours IA instantanés — aucune configuration locale requise.
Toutes les leçons de ce cours
- Mise à l’échelle horizontale des composants RAG
- Observabilité : journaux, indicateurs et traçage
- Alertes et réponse aux incidents pour l’exploitation des LLM
- Tests de charge et planification de la capacité